The long-term objectives of the project are to examine the biochemical nature, immunocytochemistry, and pathogenesis of cerebral amyloid angiopathy (CAA), a microvascular change in human brain that correlates with non-traumatic intracerebral hemorrhage, and is found with high frequency in patients with Alzheimer's disease (AD). CAA is likely to increase in importance as a public health problem because at least one common form of CAA increases in the brain with aging. The study will utilize brain tissue derived from patients with CAA-related syndromes to study the following parameters: (1) Biochemical nature of amyloid peptides in affected cerebral vessel walls, to be examined using isolation of microvessels involved by CAA, SDS polyacrylamide gel electrophoresis of CAA proteins, and their characterization using high performance liquid chromatography, determination of amino acid composition and sequence. (2) Immunocytochemical characterization of CAA, CAA-related vasculopathies and consequences of these for the brain parenchyma, by use of antibodies against peptides with the sequence(s) of the isolated proteins described above, done at light microscopic and ultrastructural levels using (respectively) an avidin-biotin peroxidase technique and protein A-gold methods. Immunohistochemistry of other AD hallmarks (e.g. senile plaques, neurofibrillary tangles) will be simultaneously examined. (3) Presence of CAA peptides or precursors in blood or cerebrospinal fluid (CSF) from patients, by use of the above derived antibodies and the Western blotting procedure--to be carried out on human serum, CSF, extracts of brain arterioles and capillaries, and microvessel-free brain tissue of patients at risk for CAA and appropriate controls. (4) Detailed immunocytochemical study of AD-related CAA using synthetic peptides representing portions of the AD amyloid precursor. (5) Studies of interaction of the AD amyloid precursor with isolated microvessels (capillaries and arterioles from AD or control brain), and cultured cells derived from human brain microvessels. All phase of the application address the issues of the pathogenesis of subtypes of CAA, the relationship of CAA to blood-brain barrier breakdown and AD.